Hi,
One idea would be to ask the ISP, and maybe pay them a bit more for the additional workload in handling the complaints. One of our ISPs has decided to simply blackhole all complaints coming from Irdeto/IP-Echelon.
The other choice is to use a more restricted exit policy, like this one: https://trac.torproject.org/projects/tor/wiki/doc/ReducedExitPolicy
It allows many relevant ports to exit, but will cut down DMCA complaints to almost zero since it does not allow random ports.